Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

tests/unit/presentation/components/Code/CodeButtons/Save/Instructions/Data/InstructionsBuilder.spec.ts

@@ -1,22 +1,18 @@
 import { describe, it, expect } from 'vitest';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import { IInstructionsBuilderData, InstructionsBuilder, InstructionStepBuilderType } from '@/presentation/components/Code/CodeButtons/Save/Instructions/Data/InstructionsBuilder';
-import { itEachAbsentObjectValue } from '@tests/unit/shared/TestCases/AbsentTests';
 import { IInstructionInfo, IInstructionListStep } from '@/presentation/components/Code/CodeButtons/Save/Instructions/InstructionListData';
 
 describe('InstructionsBuilder', () => {
   describe('withStep', () => {
-    describe('throws when step is missing', () => {
-      itEachAbsentObjectValue((absentValue) => {
-        // arrange
-        const expectedError = 'missing stepBuilder';
-        const data = absentValue;
-        const sut = new InstructionsBuilder(OperatingSystem.Linux);
-        // act
-        const act = () => sut.withStep(data);
-        // assert
-        expect(act).to.throw(expectedError);
-      });
+    it('returns itself', () => {
+      // arrange
+      const expected = new InstructionsBuilder(OperatingSystem.Android);
+      const step = () => createMockStep();
+      // act
+      const actual = expected.withStep(step);
+      // assert
+      expect(actual).to.equal(expected);
     });
   });
   describe('build', () => {
@@ -66,18 +62,6 @@ describe('InstructionsBuilder', () => {
       expect(true);
       expect(actual).to.equal(expected);
     });
-    describe('throws when data is missing', () => {
-      itEachAbsentObjectValue((absentValue) => {
-        // arrange
-        const expectedError = 'missing data';
-        const data = absentValue;
-        const sut = new InstructionsBuilder(OperatingSystem.Linux);
-        // act
-        const act = () => sut.build(data);
-        // assert
-        expect(act).to.throw(expectedError);
-      });
-    });
   });
 });